For every Majorana DM bilinear we can use the Majorana condition to
replace \(\chi \)  with its charge conjugate (see, e.g.,
[1]}). A dark matter bilinear that is odd under
charge symmetry can then be dropped from the operator basis in the
case of Majorana DM, eliminating DM vector and tensor currents (the
covariant derivatives acting within the bilinear can change this). The
list of these operators is given explicitly at the end of
Section REF . In complete analogy, the operators listed
at the end of Section  vanish for real scalar
DM.
